Keep getting recurring "blocked infection" but scan shows hard drive is clean?

Been getting the following avast screen or similar over the last few weeks. Tried running avast scan and other malware scanners but hard drive comes back clean. Also had two strange attempts from programs not recognized (netbiosd and gamed) to be granted ability to accept incoming connections. (second photo, request was denied) Thoughts?

URL:Mal = IP and/or domain is blocked/blacklisted.

Eddy,
Thanks for the reply! Do you think its something internal or external. What could be triggering this event?

I would think you caught some Junkware but im not sure.

Maybe you can track the bugger down with one of these FREE tools:

https://objective-see.com/products.html

Take a look at this thread. I had success eliminating this alert by deleting many of my “Favorites” bookmarks in Safari.

https://forum.avast.com/index.php?topic=191151.15